Preheat your oven to 350°F (175°C) and line the baking pan with parchment paper.

Sift together the flour, salt, and cocoa powder in a bowl and set aside.

In a saucepan, combine butter, canola oil, and 1/2 cup of sugar. Heat until melted, then let cool briefly.

Whisk together the eggs and remaining sugar until smooth, then stir in vanilla extract.

Gradually whisk the warm butter mixture into the eggs to avoid cooking the eggs.

Fold the dry ingredients into the wet mixture until just combined.

Fold in chocolate chips and any desired mix-ins carefully.

Pour the batter into the prepared pan and smooth the top.

Bake for 30 minutes for a 9-inch pan or 40 minutes for an 8-inch pan. Check for doneness.

Cool the brownies in the pan for 2 hours before slicing into squares.